1. Field of the Invention
The present invention relates to an in-vehicle emergency call apparatus that switches an operating power supply unit from a main battery in a vehicle to an auxiliary battery and transmits an emergency call signal to a service center when an emergency occurs.
2. Description of Related Art
An in-vehicle emergency call apparatus that switches an operating power supply unit from a main battery in a vehicle to an auxiliary battery and transmits an emergency call signal to a service center when, for example, an accident occurs is described in Japanese Patent No. 3700417.
FIG. 5 is a block diagram illustrating a schematic configuration of a conventional in-vehicle emergency call apparatus 1 like that disclosed in Japanese Patent No. 3700417. The in-vehicle emergency call apparatus 1 is described with reference to FIG. 5. When an occurrence of, for example, a vehicle accident causes airbag inflation signals to be input to an emergency notification detection unit 2 from an airbag electronic control unit (ECU) 3, the emergency notification detection unit 2 outputs a power supply switch signal to a power supply switch unit 4 and an emergency notification detection signal to a control unit 5. When the power supply switch signal is input to the power supply switch unit 4, a switch 4A is switched from OFF corresponding to a solid line in FIG. 5, to ON corresponding to a dashed line in FIG. 5. Then, the power supply switch unit 4 switches an operating power supply unit for supplying operating power from a main battery 6, which is installed in the vehicle, to an auxiliary battery 7. An electric power supply unit 8 supplies electric power from the auxiliary battery 7 as the operating power to the emergency notification detection unit 2, the control unit 5, and a radio-communication unit 9. When the control unit 5 receives the emergency notification detection signal from the emergency notification detection unit 2, the control unit 5 outputs an emergency call command signal to the radio-communication unit 9 and causes the radio-communication unit 9 to sent the emergency call signal to a service center through a wide area communication network.
In the above configuration, the electric power supply unit 8 is configured to supply the operating power to units such as the emergency notification detection unit 2, the control unit 5, and the radio-communication unit 9 through an electric power supply line system 11. If supplying electric power from the main battery 6 to the units is interrupted, the units are configured to operate on electric power supplied from a stored voltage of a capacitor 12, until the auxiliary battery 7 starts supplying electric power.
In the above configuration however, when the emergency notification detection unit 2 successively detects or receives multiple detection signals such as airbag inflation signals within a predetermined period, the emergency notification detection unit 2 outputs the power supply switch signal and the emergency notification detection signal to prevent a glitch in an emergency call operation. Further, since the radio-communication unit 9 consumes relatively more electric power as compared to the emergency notification detection unit 2 and the control unit 5, the capacitor 12 should have a large capacitance.
As shown in FIG. 6A to FIG. 6F, when the capacitor 12 rapidly discharges depleting the stored voltage before the emergency notification detection unit 2 receives the multiple airbag inflation signals in the predetermined period, the emergency notification detection unit 2 halts or otherwise becomes inoperative. In the above case, the emergency notification detection unit 2 cannot output the power supply switch signal and the emergency notification detection signal; thus, the operating power supply unit is not switched from the main battery 6 to the auxiliary battery 7, and the emergency call signal is not appropriately sent to a service center 10. Therefore, it is likely in some cases that an emergency call operation including switching an operating power supply unit for providing operating power and transmitting the emergency call signal is not appropriately carried out.